System for testing ethernet paths and links without impacting non-test traffic

ABSTRACT

A system for testing Ethernet paths or links without adversely impacting non-test traffic. The system includes a test traffic generator that includes a scheduler that determines when a new test packet is generated. The test traffic generator includes a packet creator that builds a test packet and a transmitter for transmitting the test packet via the Ethernet path or link. The packet creator sends the test packet to the transmitter. The traffic generator includes a transmit credit block coupled to the transmitter or to the scheduler. The transmit credit block stores an amount of credits representing a number of bytes that are available to transmit and decrements the amount each time a non-test packet is communicated via the Ethernet path or link.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/381,664, filed Apr. 11, 2019, now allowed, which is a continuation ofU.S. patent application Ser. No. 15/651,773, filed Jul. 17, 2017, nowU.S. Pat. No. 10,305,737, which is a continuation of U.S. patentapplication Ser. No. 14/446,708, filed Jul. 30, 2014, now U.S. Pat. No.9,742,579, which is a continuation of and claims priority to U.S. patentapplication Ser. No. 13/293,199, filed Nov. 10, 2011, now U.S. Pat. No.8,824,312, which is a continuation of and claims priority to U.S. patentapplication Ser. No. 12/209,345, filed Sep. 12, 2008, now U.S. Pat. No.8,139,494, which claims the benefit of U.S. Provisional PatentApplication No. 60/993,622, filed Sep. 13, 2007, each of which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

This invention relates generally to testing of Ethernet systems, and,more particularly, to systems for testing Ethernet paths and linkswithout impacting non-test traffic.

BACKGROUND OF THE INVENTION

As depicted in FIG. 1, an Ethernet link 11 is a connection between twoadjacent Ethernet devices 10A or 10B, while an Ethernet path 13, asdepicted in FIG. 2, is a connection between two Ethernet devices 10A or10B via a network 12 composed of multiples links, which may or may notbe using Ethernet. The Ethernet device 10A, 10B, may be a networkelement device, such as a router, a switch, etc. or could be a simplerdevice, such as a personal computer (PC) or other terminal device. Incase of a network element device, the Ethernet traffic may originatefrom or be destined for the device itself or from other devices behindit. The Ethernet link 11 and the Ethernet path 13 can be called anEthernet circuit. The testing of an Ethernet circuit includestransmitting test traffic from one location toward an Ethernet device10A or 10B. The test location may be anywhere on the Ethernet circuit.Test traffic reception processing, which may include validation,counting, bandwidth determination, etc., is not necessary, albeituseful, for the purpose of this invention.

The test traffic uses specified attributes (e.g., Ethernet ethertype,data pay 10 Ad, priority parameters, IP or MAC addresses, packet size,etc.) and specified transmission characteristics (such as bandwidth,burst size, test duration, etc.). The goal of the testing is to verifythe ability of the Ethernet link 11 or path 13 to successfully conveyEthernet frames from one device 10A or 10B to another Ethernet device10B or 10A under the specified conditions (packet attributes andtransmissions characteristics). The traffic attributes or transmissioncharacteristics used for a given test session may be set to any desiredvalue as necessary but the operation of this invention does not dependon any setting. The Ethernet link 11 or path 13 is said to be in-use orin-service when traffic other than the test traffic is present on thesaid Ethernet link 11 or path 13 at the location where test traffic istransmitted.

SUMMARY OF THE INVENTION

Aspects disclosed herein relate to the testing of an Ethernet link 11 orEthernet path 13, while it is being used by non-test traffic. In atypical test scenario, not using this invention, the non-test traffic isinterrupted so that the validity of the test is not impaired. As aresult, such a test is only performed at the installation time of theEthernet link 11 or path 13 or when the Ethernet circuit is not in useor during non-normal business hours (night, week-ends, etc.). It is,however, desirable to be able to perform a test while non-test trafficis present, because problems (to be detected by the test) usually occurat the time of normal operation of the Ethernet circuit. But the testshould be conducted in such a way that the normal non-test traffic isnot affected. This invention relates to the methods and techniques usedto perform a test while not impairing or impacting the normal operationof the non-test traffic. Impact or impairment occurs when non-testtraffic is either excessively delayed or prevented from being deliveredfrom one Ethernet device 10A or 10B to the other Ethernet device 10B or10A due to the presence of test traffic. It is possible to execute atest, with non-test traffic present, without the use of this inventionhowever some of the non-test traffic may either be dropped orexcessively delayed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood from the following descriptionof preferred embodiments together with reference to the accompanyingdrawings, in which:

FIG. 1 is a function block diagram of two Ethernet devices connected viaan Ethernet link;

FIG. 2 is a functional block diagram of an Ethernet path between twoEthernet devices;

FIG. 3 is a functional block diagram of a test traffic generator in anEthernet network comprising Ethernet links, an Ethernet path, andEthernet devices;

FIG. 4 is a functional block diagram of a transmit generator and itsfunctional blocks including a transmit block coupled to a transmitcredit block; and

FIG. 5 is a functional block diagram of a transmit generator and itsfunctional blocks like those shown in FIG. 4 except that the transmitcredit block is responsive to a scheduler.

DETAILED DESCRIPTION

Although the invention will be described in connection with certainpreferred embodiments, it will be understood that the invention is notlimited to those particular embodiments. On the contrary, the inventionis intended to cover all alternatives, modifications, and equivalentarrangements as may be included within the spirit and scope of theinvention as defined by the appended claims.

An embodiment of the invention includes the test traffic generator 14A,14B, or 14C of FIGS. 3-5, which dynamically adapts its transmissioncharacteristics in such a way as to not impair or impact the non-testtraffic. Non-test traffic transmission characteristics (bandwidth, burstsize, duration, etc.) may be bound by a bandwidth profile of some sortor may only be limited by the physical characteristics of the Ethernetmedium (link speed, etc.).

The dynamic test traffic generator 14A may be embedded in an Ethernetdevice 10A or 10B, or it may be located adjacent to the Ethernet link 11as a generator 14B or it may be located in-line of the Ethernet link 11as a generator 14C. In the case of generator 14C, there are at least twoEthernet ports that carry non-test traffic. Generator 14C must thereforeforward non-test traffic between its ports. This function does notrelate to the operation of this invention. In all cases, the informationabout the amount of non-test traffic flowing in the same direction asthe test traffic is made available to the dynamic test traffic generator14A, 14B, 14C. As an example, if the test traffic generator 14B sendstest traffic toward the Ethernet device 10B, the information about theamount of non-test traffic flowing from Ethernet device 10A toward theEthernet device 10B is made available to the generator 14B. The Ethernetpath 13 and the network 12 may or may not be present. If the network 12and the Ethernet path 13 are not present, the two Ethernet links 11 areconnected together and form a single Ethernet link (as in FIG. 1).

The transmit generator 20 of FIG. 4 includes multiple functionalbuilding blocks, such as a scheduler 21, a packet creator 22, a transmitblock 23 and a transmit credit block 24. Other functional buildingblocks not related to this invention may be included but are notillustrated. The scheduler 21 determines when a new test packet needs tobe generated. It instructs the packet creator 22, which builds a validtest packet and sends it to the transmit block 23. The function of thetransmit block 23 depends on where the traffic generator 20 is located.In the case of the traffic generator 14A, embedded in Ethernet device10A, the function of the transmit block 23 is to sending the generatedtraffic to other functions within Ethernet device 10A. The exact scopeand operation of these other functions do not relate to this invention.In the case of the traffic generator 14C, the function of the transmitblock 23 is to send the generated traffic to other functions within thedevice. These other functions do not relate to the operation of thisinvention. In the case of the traffic generator 14B, the transmit block23 includes an Ethernet port and is responsible for sending the Ethernettest packet on the Ethernet link 25 attached to it. Two differentpreferred embodiments are illustrated in FIGS. 4 and 5.

In the case of FIG. 4, the transmit block 23 queries the transmit creditblock 24 and transmits a test packet if sufficient credits areavailable. Credits represent the number of bytes to transmit. Headers,preamble and other Ethernet frame fields, such as the inter-frame gap,may be included in the credit count depending on the mode of operationof the bandwidth associated with the test. As an example, a layer 2 testincludes at least Ethernet headers but not the inter-packet gap. If atransmission occurs, the appropriate amount of credit is debited fromthe transmit credit block 24. If there is not enough transmit creditavailable, the transmission is delayed until enough credit is available.The information about the amount of non-test traffic is provided to thetransmit credit block 24 via line 26. The method by which thisinformation is made available to block 24 is not relevant to theoperation of this invention. Credits are removed from the transmitcredit block 24 for each non-test packet. This effectively reduces theamount of credit available to allow transmission of test traffic. Thecredit total may become negative, due to excessive non-test traffic.This will further delay the transmission of test traffic because morecredits will need to be added before enough credit is available to startthe transmission of a test packet. Transmission credits are added to thetransmit credit block 24 using methods and techniques that are notpertinent to this invention.

In the case of FIG. 5, the scheduler 21 queries the transmit creditblock 24 and only sends a request to the packet creator 22 if sufficientcredits are available. Credits represent the number of bytes totransmit. Headers, preamble and other Ethernet frame fields, such as theinter-packet gap, may be included in the credit count depending on themode of operation of the bandwidth associated with the test. As anexample, a layer 2 test would include at least Ethernet headers but notthe inter-frame gap. If a request occurs, the appropriate amount ofcredit is debited from the transmit credit block 24. If not enoughtransmit credit is available, the request is delayed until enough creditis available. The information about the amount of non-test traffic isprovided to the transmit credit block 24 via the line 26. The method bywhich this information is made available to block 24 is not relevant tothe operation of this invention. Credits are removed from the transmitcredit block 24 for each non-test packet. This effectively reduces theamount of credit available to allow transmission of test traffic. Thecredit total may become negative, due to excessive non-test traffic.This will further delay the transmission of test traffic because morecredits will need to be added before enough credit is available to startthe transmission of a test packet. Transmission credits are added to thetransmit credit block 24 using methods and techniques that are notpertinent to this invention.

While particular embodiments and applications of the present inventionhave been illustrated and described, it is to be understood that theinvention is not limited to the precise construction and compositionsdisclosed herein and that various modifications, changes, and variationsmay be apparent from the foregoing descriptions without departing fromthe spirit and scope of the invention as defined in the appended claims.

What is claimed is:
 1. A system for testing a path in a networkcomprising: at least one pair of devices coupled via said path; at leastone test packet generator coupled to said path comprising: a schedulerto determine when a test packet is to be created; and a packet creatorto create the test packet to be transmitted on said path; wherein saidscheduler uses an amount of credits to determine when the test packet isto be created; and wherein said amount of credits are decremented eachtime a non-test packet is transmitted on the path.
 2. The system ofclaim 1, wherein the credits are incremented periodically.
 3. A methodfor testing a network path between two devices comprising: determining,based on an amount of credits, when a test packet is to be generated;and generating and transmitting said test packet on said path; andwherein said amount of credits are decremented each time a non-testpacket is transmitted on the path.
 4. The method of claim 3 wherein saidtest packet is transmitted when said amount of credits is greater than asize of said test packet.
 5. The method of claim 3 further comprisingadjusting said amount of credits when the test packet is transmitted. 6.The method of claim 3 further comprising periodically incrementing theamount of credits.